The Principles That Makes A Scanner Work

You may have wondered while you were converting documents to a digital format with your scanner exactly how it works. Whether it is a standard flatbed scanner, a barcode scanner or something like a hand held wand scanner, they all have something in common. What makes these devices tick, or bleep or whatever it is that a scanner does? What are the working principles behind a scanner?

We are here to answer these questions for you. In this piece we will cover the basics behind scanning. What are the principles behind how a scanner works and are there different types of scanners that work differently, are just the start of what we will cover. That way you will know exactly where you stand when it comes to how your scanner converts things to a digital format.

Scanners in our offices and shops

Scanners are incredibly handy devices in our offices today. They can make your administration run so much more efficiently, by ensuring that the documents you need are available in a digital format. Scanners are also an integral part of most retail outlets.

Every time you buy an item the barcode is scanned by a basic scanner. In certain industries you almost can’t work at all if you don’t have scanners in your business.

There are many different types of scanners, from flatbed scanners, to larger scanners with document feeders. There are also smaller hand held scanners as well as huge drum scanners that are used by publishers to capture high quality scans on a large scale.

A scanner is a basic input device. The key principle of a scanner is that it analyses or records the input you provide, whether it is a document of a photograph, and then coverts it to data that the computer can store and you can edit.

Key principles

When you look at a flatbed scanner, it has certain components that we can use to explain the principles of how it works, that you can also apply to other types of scanners. Other scanners may look different but almost all of them operate on the same principles with the same components.

A flatbed scanners will usually have a charged coupled device (CCD) array, some mirrors, a scan head and lamp, a glass plate, lens and filters, a belt, stabilizers, as well as a power supply. It will also have an interface where you can interact with it, both physically and via your computer.

The CCD array

The most important component in this list of items is the CCD array. This component is made up of tiny, diodes. These diodes are light sensitive and work by converting light to electricity. It basically takes light photons and convert it to electrons that can be read by programs.

The principle is quite straightforward, the brighter the light that these diodes sense, the greater the electric charge at that specific coordinate.

Light and images

The CCD array is an essential component, but it won’t be very effective if you can’t tell the diodes where the image is. The image reaches the CCD array through the use of mirrors, lenses and sensors. The configuration and set up of these elements depends on the type of scanner you have. This allows the CCD array to effectively see the input you want it to scan and covert to data.


As with any good team, you need different skills and focus areas to get the job done well. The same is true of a scanner. You need various components to function together so you can get a clear image on your PC desktop. So let’s take you through the steps that a scanning team goes through.

When you use a typical flatbed scanner, you will place a document or photo on the glass plate that is protected by the cover. You then close the cover over the document to keep any additional light out. This ensures that you get a clear image fo the document. The cover gives you a clean, uniform background. The software can understand it much more clearly and will calibrate using this as well.

The cover is not essential however, and you can remove it to scan items that don’t fit when it is closed. A book, or large image perhaps. A lamp then lights the document as it is scanned.

The entire scanning mechanism is a combination of mirrors, lamps, the CCD array and filters. These components work so well together they almost seem like they are a single element of the scanner. This single entity can be called the scan head. In some hand held scanners the scan head is the entire scanner. In flatbed scanners a motor will move it across the document.

The mirrors reflect the image to ensure that it is focused onto the lens, where the CCD array can convert it to data. Each scanner will operate is almost the same way, but some will use a single pass, where others will pass up to three times, each time with a focus on a different color in the spectrum (green, red or blue), but the final result will be more or less the same.

Another role player

As we get savvier with our technology, we also have different sensor types, especially to get scanners on the market that are less expensive. These sensors are called CIS or contact image sensors. These sensors don’t have a CCD array, but rather have red, green and blue LED’s (light emitting diodes) that make the scanners cheaper and thinner.

Although these sensors look different they still function with the same principle as above. Light is sensed and converted to an electrical charge that can be interpreted by your computer.

Final words

Hopefully this piece clarified a few things for you when it comes to the principles of a scanner. The easiest way to think about the principles behind a scanner (for us at least) is that it is a device that converts light from a document, to electricity. The electrical charge is read by your computer and interpreted so you can now have a digital copy of the photo, document or code you scanned.

Leave a Comment

Your email address will not be published. Required fields are marked *